The inspectors team, led by Swedish scientist and chemical weapons expert Ake Sellstrom, was to start its investigation Monday, a day after arriving in Damascus, U.N. Secretary-General Ban Ki-moon's office said in a statement from New York Sunday.
The 20-member team made no public comment on its arrival in the Syrian capital.
"The mission will begin its work on Monday," the statement from Ban's office said. "Further updates may be given in due course from New York.
"Please note the team will not be speaking to the media."
Syrian President Bashar Assad and rebels seeking to oust him have accused each other of deploying chemical weapons in the conflict, which is nearly 3 1/2 years old and has left more than 100,000 Syrians dead.
The accusations have included blame and counter-blame for an alleged March 19 chemical strike in the village of Khan al-Assal, near the northern city of Aleppo, which was reported to have left dozens of people dead.
The U.N. team will go to Khan al-Assal and two other locations that have not been made public.
The United Nations originally pushed for free access to investigate.
The team agreed to determine if chemical weapons were used and, if so, what type, but not to say who used them.
The Assad regime has promised to cooperate with the investigation.
In announcing the agreement for the long-delayed visit Wednesday, Ban's office said Assad's regime agreed the U.N. team could "remain in the country to conduct its activities, including on-site visits, for a period of up to 14 days, extendable upon mutual consent."
U.S. President Barack Obama declared last year the use of chemical weapons would be a "red line" that could lead to U.S. military action.
U.S. officials said June 13 they believed Assad's forces used chemical weapons "on a small scale against the opposition multiple times in the last year," killing 100 to 150 people.
But that did not lead to a significant public change in U.S. involvement in the war.
Russia, which backs the Assad regime, said at the United Nations July 9 its experts determined Syrian rebels used sarin nerve gas in Khan al-Assal.
White House spokesmen Jay Carney disputed Moscow's allegation.
Syria's opposition reported another chemical attack by the Syrian army in two Damascus suburbs Aug. 5, exposing some 400 people to alleged toxic chemical gases. It posted several videos on YouTube as evidence.